High Traffic Exposure Hurts Lung Function in Asthmatic Kids

Action Points

Explain to interested patients that this study found that in asthmatic children who live in a major border town, more exposure to traffic increases lung problems.

ATLANTA, Dec. 18 -- Among children with asthma in the border city of Ciudad Juarez, Mexico, which is heavy with traffic to and from El Paso, Tex., pollution near their homes has been associated with airway inflammation and lower lung volumes.

The results of this study "suggest that there is a chronic respiratory effect associated with exposure in close proximity to roads," reported Fernando Holguin, M.D., M.P.H., of Emory University here, and colleagues on both sides of the border. A similar study of children in El Paso is under way.

Asthmatic children had significant increases in exhaled nitric oxide and a significant decrease in FEV1 even in homes 200 meters from the road. Children were evaluated by an averaged range in road density (amount of road length in kilometers) at 50 meters, 100 meters, and 200 meters from where they lived.

For this study, conducted as part of the EPA's U.S.-Mexico Border 2012 program, the researchers recruited 200 children ages six to 12, half with asthma and half without.

Seventy-eight percent of the asthmatic children were classified as mild intermittent, 13% mild persistent, 8% moderate persistent, and 1% severe. Asthmatic children were also more likely to have atopy than nonasthmatic children (58% versus 37%).

Air pollutants -- two-week nitric oxide and 48-hour average levels of elemental carbon and particulate matter of less than 2.5 Î¼m (PM2.5) -- were measured at participating schools. Road and traffic densities were calculated at schools and at each participant's home.

For asthmatic children, Dr. Holguin and colleagues found significant associations with road density:

At the 50-meter home buffer, the increase in exhaled NO was 28% (95% CI: 3 to 60, P=0.03). Children in this buffer had an odds ratio of 1.58 (95% CI: 1.05 to 2.38) for having respiratory symptoms.

At the 100-meter home buffer, the increase in exhaled NO was 27% (95% CI: 8 to 49, P=0.005).

At the 200-meter home buffer, the increase in exhaled NO was 17% (95% CI: -2 to 40, P=0.09) and the reduction in FEV1 was -0.106 L (95% CI: -0.171 to -0.041, P=0.002).

Dr. Holguin and colleagues found no significant association between the pollutants and exhaled NO. However, exposure of asthmatic children to NO2 near school was "marginally associated" with a reduction of FEV1 (-0.020, 95% CI: -0.042 to 0.001, P=0.060).

There were no significant associations found in nonasthmatic children at any point in the study.

The investigators listed several limitations in interpreting these results. The study was underpowered, they said, to detect associations with traffic density, as they only had traffic information on 212 km out of 3,951 km of roads. Additionally, using road density as a measure of traffic-related exposure may be confounded by noise and variations in socioeconomic status, they wrote.

They also pointed potential causes for the failure to detect signiï¬cant associations with any of the air pollutants measured in the study. "This could be partly explained by our study being underpowered and by the fact that our asthmatic population was characterized by children with mild intermittent and mild persistent asthma" they wrote.

Ozone exposure was not measured in the study, although Dr. Holguin and his colleagues did not expect this to confound the results because ozone is more evenly distributed across large areas, and they found associations on both high- and low-ozone days. They did not control for any seasonal effects.

"Results from our study provide further evidence that traffic-related exposures are associated with increased airway inflammation and reduced lung function in children with asthma," the researchers wrote. "This finding could have significant public health policy implications because a significant proportion of schools in many countries are located in close proximity to major roads."

The study was supported by the CDC, the Mexico Foundation for Science, an Oakridge Institute for Science and Education fellowship, and an EPA grant.

The authors reported that they had no financial conflicts.

Reviewed by Zalman S. Agus, MD Emeritus Professor University of Pennsylvania School of Medicine

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